Optical and electronic properties of (InxGa1-x)2O3 alloys

Indium gallium oxide [(InxGa1-x)(2)O-3] alloys are of interest for a variety opto-electronic applications including photovoltaic devices owing to the ability to control properties through alloy composition. A thorough evaluation of the opto-electronic properties of (InxGa1-x)(2)O-3 (x = 0.71, 0.55, 0.45, 0.36, and 0.28) thin films is obtained by using terahertz to ultraviolet range spectroscopic ellipsometry to measure the complex dielectric function (epsilon = epsilon(1) + i epsilon(2)) spectra from 0.400 meV to 5.877 eV and the derived vibrational modes from chemical bonding, inter-band transition energies, and carrier transport properties. Optical band edges of direct and non-direct transitions increase from 3.82 to 4.14 eV and 2.96 to 3.36 eV, respectively, with decreasing In-content, whereas the carrier concentration determined from the direct electrical Hall effect and spectroscopic ellipsometry measurements decreases from similar to 10(20) to 10(18) cm(-3). Mobilities (mu(SE)), resistivities (rho(SE)), and carrier effective masses (m*(SE)) from the spectroscopic ellipsometry range from similar to 10.6 to similar to 66.8 cm(2) V-1 s(-1), 2.3 x 10(-3), to 47.1 x 10(-3) Omega cm, and 0.308 to 0.397 m(e), respectively. mu(SE) and rho(SE) are compared to those obtained from the direct electrical Hall effect and four-point probe measurements with discrepancies attributed to principles of measurement techniques. Spectroscopic ellipsometry determined parameters are representative of properties within localized regions, whereas direct electrical measurements are influenced by a greater degree of charge carrier scattering due to longer path lengths of travel.